The present invention relates to a process for forming photoresist images which is used in preparation of a printed wiring board, a lithographic press plate and the like.
Hitherto, for forming photoresist images, there is applied a laminate film in which a photosensitive layer is formed on a light-permeable support such as a polyethylene terephthalate film, and if necessary, a protective film such as a polyethylene film is laminated on the photosensitive layer. In forming photoresist images, the protective film is peeled off from the laminate film, the photosensitive layer is stuck to a substrate such as a copper plate and is imagewise exposed to light through the support, the support is then peeled off and the exposed resist is developed by washing away the unexposed area with a solvent or an aqueous solution of an alkali which results in a substrate bearing a resist image on its surface.
However, a film such as a terephthalate film used as a light-permeable support often sticks to the hand on peeling off and is absorbs dust owing to static electricity. Also, it is very difficult to peel off the support from a substrate automatically.
It is proposed, as disclosed in Japanese Unexamined Patent Publication (Tokkyo Kokai) No. 140341/1981, to employ a water-soluble polyvinyl alcohol resin film as a support for the purpose of effectively removing the support film from the substrate. This support film can be easily removed by washing away with water or an aqueous alkali solution without mechanically peeling off. However, the polyvinyl alcohol resin inevitably accumlates in the washing water and the concentration of the polyvinyl alcohol resin increases gradually, since the water or the aqueous alkali solution is reused circularly. When the concentration reaches a high concentration over 3 to 5% by weight, effective removal can be no longer carried out because the rate of dissolving the polyvinyl alcohol resin is remarkably lowered, and the washing water is apt to foam. On the other hand, removal of the polyvinyl alcohol resin from washing water is uneconomical.
It is an object of the present invention to eliminate the disadvantages of the conventional process for forming photoresist images.
A further object of the invention is to provide a process for forming photoresist images useful for the preparation of a printed wiring board, a lithographic press plate and the like, in which a support film is easily washed away by water or an aqueous alkali solution from a laminate film after exposure of a photosensitive layer.
These and other objects of the present invention will become apparent from the description hereinafter.